arm64: dts: renesas: r8a779f0: Add missing hypervisor virtual timer IRQ

Add the missing fifth interrupt to the device node that represents the
ARM architected timer.  While at it, add an interrupt-names property for
clarity,

Fixes: c62331e8 ("arm64: dts: renesas: Add Renesas R8A779F0 SoC support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/46deba1008f73e4b6864f937642d17f9d4ae7205.1718890849.git.geert+renesas@glider.be